Hydraulic pressure transmitting fluid



Patented June 19,1956

dice

2,751,356 HYDRAULIC PRESSURE TRANSMHTTING FLUID Chester M. White and Arthur W. Sawyer, Rochester, N. Y., assignors to Genesee Research Corporation, Rochester, N. Y., a corporation of New York No Drawing. Application April 17, 1953, Serial No. 349,543

16 Claims. (Cl. 252-75) The present invention relates to a new and improved hydraulic pressure transmitting fluid which, while not limited thereto, is particularly adapted for use as a hy draulic medium in hydraulic brake systems, hydraulic presses, and other fluid pressure actuated mechanisms.

In spite of extended research in an effort to develop substitutes, castor oil is still widely used today as a base or lubricant in hydraulic pressure transmitting fluids. Possibly the greatest drawback and disadvantage attending the use of castor oil for this purpose is its tendency to oxidize and form a thick, tacky film on the moving parts of the hydraulic pressure system in which his employed. An almost equally serious disadvantage of castor oil base fluids is their comparatively low water tolerance. Straight castor oil fluids may be separated into phases due to the presence, of water of condensation.

The foregoing and other disadvantages of castor oil were obviated by the practice of the invention described and claimed in U. S. Patent No. 2,499,551 issued on March 7, 1950 to Chester M. White, one of the co-inventors herein. -In this White patent there was disclosed a new class of materials which could be substituted for castor oil. These new materials, which are designated as polymerized alkylene glycols, are known as synthetic lubricants when employed in this environment. Thesepolymerized alkylene glycols should have average molecular Weights ranging from about 180 to 420. While it is possible to employ a polymerized alkylene glycol, or a mixture of polymerized alkylene glycols per se, it is in most cases desirable and preferable to dilute the polymer with a diluent or solvent.

More particularly, the foregoing patentee contemplated the use of polymerized lower alkylene glycols of varying molecular weight such as polymerized ethylene glycols of varying molecular weight. Particularly suitable in hydraulic fluid use as synthetic lubricants are the following polymers having the physical constants indicatedz' Polymerized Ethylene Glycols In addition to the polymerized alkylene glycols de-' scribed hereinabove, other synthetic lubricants have been found suitable, such as hexanetriol l, 2, 6,tributoxyethyl phosphate, tributoxyethoxy ethyl phosphate, and tricresyl phosphate. it is to be understood, therefore, that the term synthetic lubricant as used herein covers the foretype and other synthetic type brake fluids.

going and other synthetic lubricants useful in this environment.

These synthetic lubricants, when compounded with conventional diluents or solvents, and inhibitors and antioxidants, obviate the aforesaid difliculties encountered in castor oil use, but one disadvantage attending these synthetic lubricant bases is their comparatively high cost. it is an object of the present invention, therefore, to produce a hydraulic pressure transmitting fluid which not only obviates the disadvantages of castor oil base fluids but which is cheaper to produce than known fluids containing synthetic lubricant bases.

It has now been found, in accordance with the present invention, that up to 50% of the synthetic lubricant base ordinarily employed in these formulations may be replaced by tall oil soap which is relatively cheap to manufacture and which has been found to possess excellent lubricating and coupling action. More particularly, the tall oil soap contemplated in the practice of the present invention is a potassium soap made by the simple inter-reaction of tall oil and potassium hydroxide. Other hydroxides may be employed but potassiuum hydroxide is preferred. It should also be pointed out that the tall oil-potassium hydroxide soap useful in accordance with the present invention may be either preformed before incorporation with the remaining synthetic lubricant base and solvents, or the finished fluid may be compounded by simply including the tall oil and the potassium hydroxide in the synthetic lubricant and solvents making up the desired formulation. In this way the tall oil-potassium hydroxide soap will be formed in situ.

It should be further pointed out that while castor oil soap has been employed heretofore for its coupling action, the tall oil-potassium hydroxide soap of the pres ent invention is decidedly superior in this respect to the castor oil soap. In addition, the tall oil-potassium hydroxide soap is superior to castor oil soap in that the tall oil soap is more miscible with water than is castor oil soap. Moreover, it has been found that one can replace, with tall oil-potassium hydroxide soap, up to 50% of the amount of synthetic lubricant base ordinarily required to yield a satisfactory evaporation residue and yet produce a fluid which exhibits satisfactory lubricity.

The use of tall oil-potassium hydroxide soap in conjunction with synthetic lubricants oifers a new source of currently low priced lubricant which is superior to vegetable oils for use in hydraulic brake fluids, in that the residue from standard evaporation tests is a liquid lubricant at 32 F. while vegetable oils tend to become gummy or solid under similar testing.

The tall oil-potassium hydroxide soap-synethtic lubria cant imparts advantageous properties to hydraulic brake fluids. When held at low temperatures of 40 to 60 F., these fluids show less tendency to precipitate or become cloudy than do castorgo'ilba'sed fluids. Such fluids have excellent miscibility with other hydraulic brake fluids and have outstanding ability to assimilatemoisture;

By proper selection of synthetic lubricant andsolvent mixturealong with the tall oil-potassium hydroxide soap, it is possible to compound a hydraulic brake fluid which is miscible with glucose type,vglycer ine type, castor oil Such fluids also act as coupling agents for non-miscible liquids, such as castor oil type 'fluidand water mixture. I

In-compounding-the improved hydraulic pressure trans mitting fluid of the present invention, the synthetic lubri- .cant-tall oil soap is included with solvents and inhibitors,

antioxidants and water (when the latter are deemed necessary), in the following approximate proportions:

Percent Synthetic lubricant 5.0 to 30.0 Tall oil soap 5.0 to 30.0 Solvents 40 to 89.8 Inhibitors and antioxidants 0.2 to 2.0 Water 0.0 to 8.0

As diluents or solvents one may employ glycols, alcohols and glycol ethers.

Among the glycols and alcohols found useful are ethylene glycol, propylene glycol, butylene glycols, tetraethylene glycol, methoxy, methoxy ethanol, ethoxy triglycol, butoxy triglycol, propanol, isobutanol, n-butanol and methyl isobutyl carbinol.

Illustrative of the glycol ethers which may be employed as diluents or solvents are the methyl, ethyl, propyl, butyl, etc. ethers of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol and tetrapropylene glycol. Included in the forernentioned glycol ethers are such materials as the Carbitols and the Cellosolves.

It is to be understood, of course, that mixtures of any of the foregoing glycols, alcohols and glycol ethers may be employed as solvents or diluents.

Also, there may be employed an alcohol type solvent which consists predominantly of and 6 carbon alcohols containing relatively small amounts of 6 and 7 carbon ketones.

When desired any inhibitors and/ or antioxidants may be employed. As inhibitors one may employ, diisopropylamine nitrite, mercaptobenzothiazole, sodium salt, orthobenzoicethanolamine, di-isopropylamine nitrite, triethanolamine ricinoleate and phenyl morpholine.

While exemplary of antioxidants which may be employed are phenyl alpha naphthylamine, hydroquinone, tertiary butyl catechol, methyl diteritiary butyl phenol, p,p-isopropylidene bisphenol.

Exemplary of specific brake fluid formulations ernploying the synthetic lubricant-tall oil soap base of the present invention are the gollowing:

Moderate duty brake fluid In the above formula, the ethylene glycol-2,3 butylene glycol combination may be replaced by 17.000% ethylene glycol.

Heavy duty brake fluid A Percent Tall oil ..L 10.22 Potassiumhydroxide (90%) 2.10 Polymerized ethylene glycol (MW 200) 16.00 Ethylene glycol 20.00 Ethyl ether of diethylene glycol 10.00 Butyl ether of ethylene glycol 21.90 Butoxytriglycol 19.48 Inhibitors and antioxidants 0.30

The above noted brake fluid formulations possess the following physical constants:

Moderate Heavy Duty SAE Test Methods Duty A Viscosity:

at 130 F. in 08.... 0.8. at -20 F. in cs. at -40 F. in cs. 1,092. Boiling Point, F 331. Flash Point, I (000). Evaporation, (percent).-. 21.8 30.3.

(Character) satisfactory. satisfactory. Rubber Swelling (inches) .043 0.021. Corrosion satisfactory. satisfactory. Stability ..do Do. Compatability do D0. Lubrication -do Do.

Examples of fluids based on other synthetic lubricant combinations are as follows:

Fluid B Percent Tall oil 7.50 Potassium hydroxide 1.57 Hexanetriol 1,2,6 10.50 Ethylene glycol 25.00 Ethyl ether of diethylene glycol 25.00 Methyl isobutyl carbinol 5.00 Butyl ether of ethylene glycol 25.00 Antioxidants and inhibitors 0.43

Fluid C Percent Tall oil 7.50 Potassium hydroxide (90%) 1.57 Tributoxy ethyl phosphate 10.50 Ethylene glycol 25.00 Ethyl ether of diethylene glycol 35.00 Methyl isobutyl carbinol 5.00 Butyl ether of ethylene glycol 15.00 Antioxidants and inhibitors 0.43

The foregoing fluids are completely miscible with castor oil fluids. No separation into phases takes place after the fluids .are held at --40 C. for 24 hours.

A further advantage of the fluids of the present inventron resides in their miscibility with other commercial fluids 1n common use in brake systems today. They also have good low temperature characteristics.

The fluids have good water tolerance. Corrosion of the various metals in the hydraulic system can be held under control by means of the usual inhibitors. Viscositles at F. and at 40 F. establish a viscositytemperature curve with a satisfactory slope.

In order to illustrate the miscibility of tall oil soap brake fluid compared to commercial brake fluids, reference 1s made to the following test data:

O:=.Not miscible inl Proportions.

Formulas used in above tests Test fluid: Percent by Weight Tall oil KOH (90%) 2 Polymerized ethylene glycol (MW200) Ethylene glycol Ethyl ether of diethylene glycol 43 Butyl ether of ethylene glycol 10 l 100 Glucose type:

Corn syrup 33.3 Water 33.3 S. D. 3-A alcohol 33.3

100 Glycerine type:

C. P. glycerine 45 Water 5 S. D. 3-A alcoho 50 100 Castor oil type:

#1 Castor oil S. D. 3-A alcohol 70 100 What is claimed is:

1. A hydraulic pressure fluid consisting essentially of 5.0% to 30% of a synthetic lubricant from the group phosphate, to 5.0 to 30% of a tall oil-potassium hydroxide soap and 40% to 89.9% of a solvent from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of synthetic lubricant.

. 2. A hydraulic pressure fluid consisting essentially of the following ingredients in the approximate percentages indicated:

said solvents being selected from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of synthetic lubricant.

3. A hydraulic pressure fluid consisting essentially of 5.0% to 30% of a polymerized ethylene glycol having a molecular Weight of from 180 to 420, 5 .0 to 30% of a tall oil-potassium hydroxide soap and 40% to 89.9% of a solvent from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of polymerized ethylene glycol.

4. A hydraulic pressure fluid consisting essentially of 5.0% to 30% of a polymerized ethylene glycol having an average molecular weight of 200, 5.0 to 30% of a tall oil-potassium hydroxide soap and 40% to 89.9% of a solvent from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of polymerized ethylene glycol.

glycols and glycol ethers,

5. A hydraulic 5.0% to 30% of hexanetriol 1, 2, 6, 5.0 to 30% of a tall oil-potassium hydroxide soap and 40% to 89.9% of a solvent from the group consisting of aliphatic alcohols,

the amount of soap in no instance exceeding the amount of hexanetriol 1, 2, 6.

6. A hydraulic pressure fluid consisting essentially of 5.0% to 30% of tn'butoxyethoxy ethyl phosphate, 5.0 to 30% of a tall oil-potassium hydroxide soap and 40% to 89.9% of a solvent from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of tributoxyethoxy ethyl phosphate.

7. A hydraulic pressure fluid consisting essentially of 5.0% to 30% of tributoxyethyl phosphate, 5.0 to 30% of a tall oil-potassium hydroxide soap and 40% to 89.9% of a solvent from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of tributoxyethyl phosphate.

8. A hydraulic pressure fluid consisting essentially of 5.0% to 30% of tricresyl phosphate, 5.0 to 30% of a tall oil-potassium hydroxide soap and 40% to 89.9% of a solvent from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of tricresyl phosphate.

9. A hydraulic pressure fluid consisting essentially of the following ingredients in the approximate percentages indicated: 7

Percent Polymerized ethylene glycol having an average molecular weight of 200 5.0 to 30.0 Tall oil-potassium hydroxide soap 5.0 to 30.0 Solvents 40 to 89.8 Inhibitors and antioxidants 0.2 to 2.0 Water 0.0 to 8.0

said solvents being selected from the aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of polymerized ethylene glycol.

10. A hydraulic pressure fluid consisting essentially of the following ingredients in the approximate percentages indicated:

group consisting of Percent Hexanetriol l, 2, 6 5.0 to 30.0 Tall oil-potassium hydroxide soap 5.0 to 30.0 Solvents 40 to 89.8 Inhibitors and antioxidants 0.2 to 2.0 Water 0.0 to 8.0

said solvents being selected from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of hexanetriol 1, 2, 6.

11. A hydraulic pressure fluid consisting essentially of the following ingredients in the approximate percentages said solvents being selected from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of tributoxyethoxy ethyl phosphate.

12. A hydraulic pressure fluid consisting essentially of the following ingredients in the approximate percentages indicated:

Percent Tributoxyethyl phosphate 5.0 to 30.0 Tall oil-potassium hydroxide soap 5.0 to 30.0 Solvents 40 to 89.8 Inhibitors and antioxidants 0.2 to 2.0 Water 0.0 to 8.0

pressure fluid consisting essentially of said solvents -being selected from the group consisting of aliphatic alcohols, ,glycols and glycol ethers, the amount of soap in no instance exceeding the amount of tributoxyethyl phosphate.

13. A hydraulic pressure fiuid consisting essentially of the following ingredients in the approximate percentages indicated:

Percent Tricresyl phosphate 5.0 to 30.0 Tall oil-potassium hydroxide soap 5.0 to 30.0 Solvents 40 to 89.8 Inhibitors and antioxidants 0.2 to 2.0 Water 0.0 to 8.0

said solvents being selected from the group consisting of aliphatic alcohols, glycols and glycol ethers, the amount of soap in no instance exceeding the amount of tricresyl phosphate.

14. A hydraulic pressure fluid consisting essentially of the following ingredients in the approximate percentages indicated:

15. A hydraulic pressure -fluid consisting essentially of the following ingredients in the approximate percentages indicated:

Percent Tall oil 7.50 Potassium 'hydroxide 1.57 Hexanetriol 1, 2, 6 10.50 Ethylene glycol 25.00 Ethyl ether of diethylene glycol 25.00 Methyl isobutyl carbinol 5.00 Butyl ether of ethylene glycol 25 .00 Antioxidants and inhibitors 0.43

16. A hydraulic pressure fluid consisting essentially of the following ingredients in the approximate percentages indicated:

Percent Tall oil 7.50 Potassium hydroxide 1.57 Tributoxy ethyl phosphate 10.50 Ethylene glycol 25.00 Ethyl ether of diethylene glycol 35.00 Methyl isobutyl carbinol 5.00 Butyl ether of ethylene glycol 15.00 Antioxidants and inhibitors; 0.43

References Cited in the file of this patent UNITED STATES PATENTS 2,238,045 Fulton Apr. 15, 1941 2,345,585 Clark et al Apr. 4, 1944 2,367,462 Farber Jan. 16, 1945 2,499,551 White Mar, 7, 1950 

1. A HYDRAULIC PRESSURE FLUID CONSISTING ESSENTIALLY OF 5.0% TO 30% OF A SYNTHETIC LUBRICANT FROM THE GROUP CONSISTING OF A POLYMERIZED ETHYLENE GLYCOL HAVING A MOLOCULAR WEIGHT OF FROM 180 TO 420, HEXANETRIOL 1,2,6, TRIBUTOXYETHYL PHOSPHATE, TO 5.0 TO 30% OF A TALL PHATE AND TRICRESYL PHOSPHATE, TO 5.0 TO 30% OF A TALL OIL-PATASSIUM HYDROXIDE SOAP AND 40% TO 89.9% OF A SOLVENT FROM THE GROUP CONSISTING OF ALIPHATIC ALCOHOLS, GLYCOLS AND GLYCOL ETHERS, THE AMOUNT OF SOAP IN NO INSTANCE EXCEEDING THE AMOUNT OF SYNTHETIC LUBRICANT. 